صحيح مسلم

'A'isha (Allah be pleased with her) reported that there came Aflah the brother, of Abu'l-Qu'ais, who sought her permission (to enter) after seclusion was instituted, and AbuQu'ais was the father of 'A'isha by reason of fosterage. 'A'isha said: By Allah, I would not permit Aflah unless I have solicited the opinion of Allah's Messenger (ﷺ) for Abu Qulais has not suckled me, but his wife has given me suck. 'A'isha' (Allah be pleased with her) said: When Allah's Messenger (ﷺ) entered, I said: Allah's Messenger, Aflah is the brother of Abu'l-Qulais; he came to me to seek my permission for entering (the houst). I did not like the idea of granting him permission until I had solicited your opinion. Thereupon Allah's Messenger (ﷺ) said: Grant him permission. 'Urwa said it was on account of this that 'A'isha used to say. What is unlawful by reason of consanguinity is unlawful by reason of fosterage.